Perceptual computing (e.g., future computing) may include Projected Touch Surface (PTS) interfaces. PTS may use a projector to project user interface elements on a surface, such as a desk or a table. Because the surface itself may not be able to accept input, the PTS may use other sensors to observe interactive behaviors and use these as inputs. For example, the PTS may include a depth sensor to identify fingers (e.g., finger tips) moving (or being positioned) on or around the projected user interface to determine interactions with the interface.